Search PubMed⌕ Search

Biomedical subjects

H M Cheng

Publications and source records attributed to H M Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1994

Magnetic resonance imaging of the lacrimal drainage system.

BACKGROUND: Magnetic resonance imaging (MRI) has excellent spatial and soft tissue resolution in the periocular and orbital region, especially when combined with surface coil techniques. Other methods, including computed tomography, dacryocystography, and dacryoscintigraphy provide limited information in the area of the lacrimal drainage system. Magnetic resonance imaging was used in conjunction with other imaging modalities to compare the anatomic detail and clinically relevant information obtained about various pathologic processes in the lacrimal drainage area. METHODS: Patients with a variety of lacrimal drainage disorders underwent MRI with either head or surface coils. Contrast agents also were used in selected cases. Seven case reports are presented. RESULTS: Magnetic resonance imaging provided detailed information about local anatomy, extent of pathology, and, in some cases, etiology of the pathology. CONCLUSIONS: Magnetic resonance imaging with surface coils provides detailed soft tissue information when compared with dacryocystography and computed tomography in the area of the lacrimal drainage system. In selected cases of lacrimal drainage system pathology, MRI may provide data that affect patient management.

Abscess↗
PubMed1994

Cowden's disease: report of the first case in a Chinese.

A 19-year-old Chinese female presenting mucocutaneous manifestations including facial trichilemmomas, oral papillomatosis, and acral keratosis was diagnosed, according to the criteria proposed by Salem and Steck, as a definite case of Cowden's disease, although no members of her family were affected. The cutaneous reticulohistiocytic granuloma and congenital nystagmus of eyes that occurred in this case were new combinations in the syndrome. To the best of our knowledge, this is the first documented case of Cowden's disease in a Chinese.

Adult↗
PubMed1993

Role of the collagen-like domain of the human serum mannan-binding protein in the activation of complement and the secretion of this lectin.

Human mannan-binding protein (MBP) is a C-type serum lectin involved in an immunoglobulin-independent host defense. Recently, a common defect of immune opsonin was found to be associated with very low serum levels of MBP. This deficiency was thought to be an effect of a single base substitution in the MBP gene, which resulted in the conversion of Gly54 to Asp. In this study, three mutant MBPs were expressed in COS-1 cells and the effects of these mutations were studied. Gly54Asp-MBP and Gly57Asp-MBP were secreted into the medium almost at the same levels as the wild type MBP, but the formation of higher multimers and the activation of complement were interfered with significantly. The other mutant, in which Leu was inserted into the Gly63-Gln-Gly sequence to restore the collagen motif of the Gly-Xaa-Yaa repeat, was secreted at levels similar to that of the wild type, formed higher multimers and activated complement in a manner not significantly altered from that of the wild type. These results are discussed with regard to the molecular basis of patients with opsonic defects.

Animals↗
PubMed1993

Elevated secretory IgA antibodies to Epstein-Barr virus (EBV) and presence of EBV DNA and EBV receptors in patients with cervical carcinoma.

Epstein-Barr virus (EBV) receptors (EBV/C3d receptors) were detected, using the monoclonal antibody HB5, on 23 ectocervical and 5 endocervical biopsies of the uterine cervix. Elevated IgA titers against the viral capsid antigen and early antigen of EBV were also found in the cervical secretions from cervical carcinoma patients (83%), compared with samples from patients with cervical intraepithelial neoplasia (75%), herpes simplex virus-infected patients (0%), and gynecologic patients with nonmalignant conditions (0%). EBV DNA was present in 63% of cervical carcinoma biopsies detected by in situ hybridization. These observations suggest a positive association between EBV and carcinoma of the cervix.

Analysis of Variance↗
PubMed1993

Proton magnetic resonance spectroscopy of vitreal changes in experimental streptococcal endophthalmitis.

We used magnetic resonance spectroscopy to examine endophthalmitis in rabbits inoculated with a virulent strain of Streptococcus pneumoniae. On different days after infection, the animals were sacrificed and the vitreous isolated and examined with water-suppressed proton magnetic resonance spectroscopy. A broad resonance corresponding to the methyl envelope of lipoprotein lipids appeared 2 days after infection and persisted until the eyes developed phthisis (around 10 days postinfection). This resonance was absent in the control eye and the bacterial culture; it could be used as the marker of breakdown of blood-vitreous barrier and onset of endophthalmitis-induced changes.

Animals↗
PubMed1993

Screening for nasopharyngeal carcinoma with an ELISA using the Epstein-Barr virus nuclear antigen, EBNA 1: a complementary test to the IgA/VCA immunofluorescence assay.

An ELISA using the Epstein-Barr virus nuclear antigen 1 (EBNA 1) was found to detect selectively specific IgA in sera from patients with nasopharyngeal carcinoma (NPC). The antigen, p107, was a 20-amino acid synthetic peptide, representing a major epitope of EBNA 1.267/294 (90.8%) of NPC patients had IgA antibodies to p107 but in normal individuals, only 41/577 (7.1%) had IgA/p107. In sera from patients with other cancers, 11/77 (14.3%) had IgA/p107 reactivity. 124 IgA/VCA positive and 86 IgA/VCA negative NPC sera were also tested for IgA/p107 binding in ELISA. The majority of IgA/VCA positive sera (117) also contained IgA/p107 antibodies. Of interest was the detection of 74/86 IgA/p107 reactive sera in the IgA/VCA negative group. The results suggest that the IgA/p107 ELISA could become a useful, complementary screening assay to the IgA/VCA immunofluorescence test for detection of NPC.

Amino Acid Sequence↗
PubMed1993

Aldose reductase inhibition and the phosphorus-31 profile of the intact diabetic rat lens.

Diabetic metabolic change and response to aldose reductase inhibition in the Wistar rat lens were examined with phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. To avoid artifacts in sample preparation, we used freshly excised lenses and acquired NMR data for 20 min immediately after lens extraction. The results showed a diabetes-induced time-dependent loss of ATP and phosphorylcholine (PC), an increase in alpha-glycerophosphate (alpha-GP) and inorganic phosphate and the appearance of sorbitol-3-phosphate (S-3-P) and fructose-3-phosphate (F-3-P). Oral but not topical dosing of an aldose reductase inhibitor, 5-(3-ethoxy-4-pentyloxyphenyl)-2,4- thiazolidinedione, resulted in a positive dose-response correlation characterized by a restoration of PC, S-3-P and F-3-P to the prediabetic level; however, alpha-GP and ATP were only partially normalized. The significance of the 31P change was further discussed.

Adenosine Triphosphate↗
PubMed1993

Turner's syndrome associated with sigmoid polyp and colon cancer: report of a case.

A 49-year-old woman with 45,XO karyotype Turner's syndrome and a recent onset of loose-to-watery stool passage was found to have a sigmoid polyp and adenocarcinoma in the ascending colon. Turner's syndrome is a result of a variety of abnormalities of the X chromosome. There are reports that the risk of malignancy, both gonadal and nongonadal in origin, is increased in patients with such chromosomal defects. Although, diet and heredity play important roles in the etiology of colorectal cancer, the relationship between cancer and certain congenital defects should be taken into account.

Adenocarcinoma↗
PubMed1993

Antiphospholipid antibodies and stroke in the young--a study of three cases.

Cerebral infarction in the young is likely to be non-atheromatous. While in previous studies no cause has been found in 40% to 50% of patients, an increasing role for haemorheological factors is becoming apparent. Among these, an association between antiphospholipid antibodies (aPLs) and ischaemic cerebrovascular disease is now well-recognised. This entity has not been previously reported in Malaysian patients. In a study of 80 patients with stroke below the age of 50 years who were seen at the University Hospital, Kuala Lumpur, between January 1982 and May 1992, 3 patients with ischaemic cerebral infarction were found to have aPLs. aPLs was detected using ELISA method for anticardiolipin antibodies (aCLs), and presence of lupus anticoagulant (LA) was established by kaolin clotting time, thromboplastin inhibition test and platelet neutralisation procedure. Only 1 patient had active systemic lupus erythematous. Cerebrovascular events were recurrent in one of the 2 non-lupus patients. aPL-related stroke should be considered in young patients who have cerebral ischaemia occurring without obvious cause. More cases are likely to emerge in Malaysia with active screening.

Adolescent↗
PubMed1992

Visualization of water movement in the living rabbit eye.

Water enriched with the stable isotope 17O (H2(17)O) shortens the transverse relaxation time (T2) of protons in water and can therefore be used as the contrast agent for proton magnetic resonance (MR) imaging. This agent can be given topically or intravenously to demonstrate water movement in the eye. Topical H2(17)O (0.05-0.1 ml/eye, 10% enrichment) entered the anterior chamber within 5 min and dissipated from the chamber in a single-exponential fashion (flow-rate constant k = 0.1 min-1), principally due to an exchange with the iridic circulation. No H2(17)O was detected in the vitreous. Intravenous administration of H2(17)O (1 ml/kg, 10% enrichment) resulted in rapid entry (less than 20 min) of the agent into the aqueous chamber. Again, no H2(17)O was detected in the vitreous. The lens region, on the other hand, showed an increase in image intensity with time that reached a plateau after 40 min. Although these findings are preliminary, acetazolamide (20 mg/kg injected intravenously) appeared to affect iridic circulation, possibly through vasoconstriction. Potential application of this H2(17)O-enhanced MR imaging technique is discussed.

Administration, Topical↗
PubMed1992

High-resolution MR imaging of water diffusion in the rabbit lens.

Movement of water in the lens, specifically water diffusion, was examined with diffusion imaging and H217O-enhanced proton imaging. Diffusion imaging showed restricted water self-diffusion in the cortex which was not concurrent with the change in proton density; nevertheless it was dependent on the gradient direction and might be related to lens fiber/protein organization. The difference in water diffusion patterns between control and galactosemic cataract was subtle but distinguishable. On the other hand, intracameral H217O injection allowed visualization of water movement across the lens. In galactosemic cataracts, water diffused from the anterior cortex towards posterior cortex and into the vitreous. This pattern was not seen in the normal lens.

Animals↗